Compact stretch-straightening mechanism with gripping heads having separate upper and lower sections composed of vertical laminations



. Oct. 13, 1959 COMPAC HEA HAVING SEP COMPOSED Filed Jan. 8, 1957 ARATEOF VE UPPER AND LOWE RTICAL LAMINATI H. B. ALBERS 2,908,316TRETCH-STRAIGHTENING MECHANISM WITH RIPPING R CTIONS '7 Sheets-Sheet lOct. 13, 1959 BERS 2,908,316

COMPAC TRETCH-STRAIGHTE NG MECHANI WITH GRIPPING HEA HAVING SE RATE R ANL R SECTIONS MPOSE CO F VER L L NATIONS Filed Jan. 8, 1957 7Sheets-Sheet 2 0&1

2,908,31 6 PPING Oct. 13, 1959 H. B. ALBERS COMPACTSTRETCH-STRAIGHTENING MECHANISM WITH GRI HEADS HAVING SEPARATE UPPER ANDLOWER SECTIONS COMPOSED OF VERTICAL LAMINATIONS 7 Sheets-Sheet 3 FiledJan. 8, 1957 H. B. ALBERS COMPACT STRETCH-STRAIGHTE NING MECHANISM WITHGRIPPING HEADS HAVING SEPARATE UPPER AND LOWER SECTIONS COMPOSED 0FVERTICAL LAMINATIONS 7 Sheets-Sheet 4 Filed Jan. 8, 1957 Q v I G n OUODVa? 000 0033?? U 0): 0 0 6 0 W f aa o v v q 7 0 0 0/ v 0K0 e a Oct. 13,1959 H. B. ALBERS 2,908,316

COMPACT STRETCHSTRAIGHTENING MECHANISM WITH GRIPPING HEADS HAVINGSEPARATE UPPER AND LOWER SECTIONS COMPOSED 0F VERTICAL LAMINATIONS '7Sheets-Sheet. 5

Filed Jan. 8. 1957 m DE Oct. 13, 1959 ALBERs 2,908,316

. COMPACT STRETCH-STRAIGHTENING MECHANISM WITH GRIPPING HEADS HAVINGSEPARATE UPPER AND LOWER SECTIONS COMPOSED 0F VERTICAL LAMINATIONS FiledJan. 8, 1957 7 Sheets-Sheet 6 H. B. ALB ERS Oct. 13, 1959 COMPACTSTRETCH-STRAIGHTENING MECHANISM WITH GRIPPING HEADS HAVING SEPARATEUPPER AND LOWER SECTIONS COMPOSED OF VERTICAL LAMINATIONS '7Sheets-Sheet '7 Filed Jan. 8, 1957 NJNE lmi

United States Patent COMPACT STRETCH-STRAIGHTENING MECHA- NISM WITHGRIPPING HEADS HAVING SEP- ARATE UPPER AND LOWER SECTIONS COM- POSED OFVERTICAL LAMINATIONS Heinrich B. Albers, Malveme, N.Y., assignor toBaldwin- Lima-Hamilton Corporation, a corporation of Penn- .SylvaniaApplication January 8, 1957, Serial No. 633,129

12 Claims. ,(Cl. 153-35) This invention relates to mechanisms forstraightening metal plates, sheets or shapes which have become bent orwarped, particularly along their longitudinal axes, after being rolledor extruded. These mechanisms effect straightening of such products bystretching the material beyond the elastic limit. The conventionalstretching machine comprises a frame on which two gripping heads aremounted. One of these heads is adjustably secured to the frame so thatobjects of various lengths may be accommodated in the machine. Hydraulicpressure is applied to the other gripping head to move it away from thesecured gripping head, and thus subject to tensile force the objectbeing stretched. While tension is developed in the stretched object,compression forces will be set up in the frame.

Recently a demand has arisen for straightening sheets and plates whichare much larger and thicker than those heretofore handled in existingstretching machines. The need has arisen for machines on which plates orsheets having a width of ten feet or more and a thickness of severalinches can be stretched, and which necessitate pulling forces of amagnitude not heretofore employed. Several serious problems presentthemselves When it is attempted to adapt the present, known arrangementsto a much larger capacity. Among these are the following:

(1) Gripping head castings would become undesirably large, not onlybecause of their weight and difliculty of machining, but also because ofthe unequal stresses that are set up in such castings and the likelihoodof failure due to internal defects. It has been proposed to build up thegripper heads from a plurality of substantially C-shaped laminationswhich were arranged side by side in planes perpendicular to that of thearticle to be stretched, the laminations being bolted together. In thecase of straightening machines of very high capacities, however, each ofthese laminations becomes prohibitively large, and difiicult to handleand manufacture. Further, the throat portions of C-shaped laminationsare subject to high stress concentrations which cannot be determineddefinitely by calculation.

(2) A high capacity machine built according to the laminated design asproposed heretofore would be relatively long in certain portions thereofbecause the gripping heads were connected to cross-heads by linksextending outwardly from the gripping heads.

(3) The mechanism for shifting the adjustable gripping head posesdifficulties because of the heavy weight to be moved, the long distanceto be traversed, and the limited space available for accommodating therequired mechanism.

It is therefore one of the principal objects of this invention toprovide a high capacity straightening mechanism capable of producinglarge stretching forces, but which comprises gripping heads which can bereadily manufactured, and in which the stresses can be definitelydetermined in advance and controlled.

It is a further object to provide a high capacity 2,908,316 PatentedOct. 13, 1959 straightening mechanism in which the space required forthe gripping head connections is reduced.

It is also an object of the invention to provide a travel mechanism forthe adjustable gripping head, which is compact and can easily beconnected to the gripping head.

Further objects and advantages will become apparent in the followingdetailed description thereof.

In the accompanying drawings,

Fig. 1A is an isometric projection of the right-hand portion of ahorizontal stretch-straightening machine embodying this invention, theprojection being diagrammatic with certain details shown in a simplifiedmanner.

Fig. 1B is a view similar to Fig. 1A and showing the left-hand portionof the machine, Fig. 1B being an extension of Fig. 1A.

Fig. 2A is partly an elevation of and partly a vertical longitudinalsection through the adjustable gripping head of Fig. 1A, takensubstantially on the line 2A--2A'of Fig. 3A.

Fig. 2B is a vertical longitudinal sectionshowing the reciprocablegripping head of Fig. 1B and taken substantially on the line 2B-2'B ofFig. 313.

Fig. 2C is a continuation of the left-hand portion of Fig. 2B and showsa section taken substantially on the line 2C-2C of Fig. 3C.

Figs. 3A, 3B, and 3C are plan views, partly in section, of substantiallythe portions of the machine shown inFigs. 2A, 2B, and 2C, respectively.

Fig. 4 is an enlarged detail of the range adjustment mechanism shown atthe extreme right-hand end of Fig. 2A.

Referring to the drawings, there is shown a horizontalstretch-straightening machine for stretching plates or sheets. Thearticle to be stretched is gripped adjacent its ends in upper and lowergripping jaws 10, 10' of spaced gripping heads 20, 20. The heads areprovided with slides 11, 11 operating on rail surfaces 12, 12 on theupper faces of spaced frame members 14 and 15 extending longitudinallyof the machine and resting on the floor or base 16. The gripping head 20is adapted to be adjustably secured and locked in adjusted position bymeans of hollow pins 30 carried by the head 20 and adapted to engage inone of a series of oval openings 31 formed in longitudinally extendingcolumns or girders 34 and 35 raised above frame members 14 and 15. Thegirders 34 and 35 may be supported in a plurality of standards 36 on araised floor or base 37.

The gripping head 20 having been selectively locked in position by pins30 engaging in oval holes 31 on each side of head 20, the stretchingforce is applied to the other gripping head 20. For thispurpose, fluidunder pressure is admitted to inlets 40 (Fig. 1B) leading to cylinders41, .42, 43 on one side, and cylinders 44 (Fig. 2B), 45, 46 on the otherside. The rods of the pistons or rams of all of these cylinders arefixed in stationary cross-heads 50, 51 attached to girders 34, 35 bybolts 52 and resting on the frame members 14, 15,- one of the rams beingshown at 47 in Fig. 33. On admission of fluid under pressure, all of thecylinders at both sides will be moved outwardly (to the left, in thedrawing). The cylinders 41, 42, 43 are mounted in a lug generally shownat 60, and the cylinders 44, 45, 46 are mounted in a lug generally shownat 61, said lugs being rigidly attached to a cross-head (to be morefully described hereinafter) which in turn is a rigid part of grippinghead 20' so that the latter is caused to move with the cylinders. Asindicated in Fig. 1B, the lugs 60, 61 are supported on slides 67engaging rail surfaces 68 of the frame members 14, 15 and cooperatingwith the slides 11' on rail surfaces 12'. The pistons of the largercentral cylinders 42, 45 are provided with rod extensions 62, 63 mountedin supports 64, 65 in a fixed frame 66. The total force applied tocylinders 41, 42, 43, 44, 45, 46 is effective for moving the head 20'away from the head 20 to provide the stretching force.

The head 20' may be returned by pneumatic pressure acting on pistons orrams 70, 71 secured to cross-head 90' of head 20, said pistons operatingin cylinders 72, 73 fixed in frame 66. Said cylinders 72, 73 arecontinuously connected to a source of pneumatic pressure so that whenpressure is released in cylinders 41 to 46, the head 20 is returned bypneumatic pressure. The pneumatic pressure in these cylinders will alsoact to ,cushion the shock in case the part being stretched should break.

The gripping heads 20, 20' are designed to overcome the difficultieswhich, as pointed out in the introduction hereto, operated against theconstruction of a stretching machine of the capacity now foundessential. The gripping head construction illustrated shows separateupper and lower sections indicated generally at 80, 81 (see Fig. 2A) and80', 81' (see Figs. 1B and 2B). Each section is composed of a pluralityof spaced laminations 82, 83 and 82, 83', the spaces between thelaminations being filled by inward links 84, 84 and outward links 85,85', the links extending substantially vertically to cooperate with andconnect the laminations of upper and lower sections. The laminations andinterleaved links of upper and lower sections of both gripping heads aresecured to each other by tubular pins 86, 86' about which the sectionsmay tend to pivot under stress. In the space between upper and lowersections of gripping head 20 is positioned a cross head generallyindicated at 90, and in the space between the upper and lower sectionsof gripping head 20' is positioned a cross-head generally indicated at90'.

The cross-head 90 comprises a series of horizontal plates 91 (see Fig.3A) and vertical plates 92, which may be Welded together to form anintegral member which abuts against the inner surfaces of outward links85 and is rigidly secured to the links by means of bolts 87 and a plate88 bearing against the outer vertical faces of the links.

Each of the girders 34 and 35 is in the form of a .U having upper andlower arms 97 and resting on one of the arms facing inwardly. At both ofits sides the cross-head 90 is provided with upper and lower lateralextensions 95 extending above and below the arms 97 of each girder 34,35 and with an intermediate extension 96 extending between the upper andlower arms 97, the upper and lower extensions having circular openings93 (Fig. 2A) and the intermediate extension having circular openings 99therethrough forming bearing-surfaces for guiding and maintaining thepins 30 in their setting positions in oval openings 31 in the girders.The pins 30 are shown in the tom of cylinders movable on piston rods orstems 102, 103 secured to frames 104, 105 which are supported on theextensions 95 of cross-head 90. The cylinders 30 'are movable into andout of the upper and'lower aligned openings 31 in the upper and lowerarms 97 of the U-shaped girders 34 and 35. When the cylinders are intheir outward positions but register with a selected pair of openings31, fluid pressure is admitted through the stems 102, 103 to force thecylinders 30 together and into the openings 31, 99 where they lock thecross-head 90 (and, therefore, the gripper head 20) in position.

When it is desired to adjust the position of the gripper head 20, fluidpressure is admitted through suitable openings to force the cylinders 30outwardly out of the aligned openings 31 so that the head 20 may beshifted. For the latter purpose a threaded stem 110 is bolted to each ofthe extensions 96 at the two sides of cross-head 90 and extendsoutwardly to a cylinder 112 to which it is rigidly connected. Eachcylinder 112 is movable on a double-acting piston 119 and its rod orstem 114 which is releasably locked in position by means of a pair ofrange setting members 115, 116 movable in guides 117 formed in a head118 fixed to the outer end of stem 114, the range setting membersengaging one set of the oval openings 31 in girders 34, 35. By admittingfluid under pressure into each cylinder 112 at one side or the other ofpiston 119, the cylinders 112 (and, with it, cross-head 90, head 20, andpins 30) may be shifted through a distance equal to the stroke ofcylinders 112 relative to their stems 114.

In the case of a short article to be stretched, however, it may benecessary to shift the head 20 inwardly toward head 20' through adistance greater than the stroke in cylinder 1 12. To permit suchgreater movement a range adjustment is provided comprising said rangesetting members 115, 116. To vary the travel range, the setting membersare moved towards each other out of aligned oval openings 31; thereafterthe stems 114, together with head 118, may be moved relative to theircylinders '112 and within the arms 97 of the girders 34 and 35 to a newposition where the setting members register with a selected set ofopenings 31. The setting members are then moved outwardly into theselected openings to lock the stems 114 in the new position. To thisend, each setting members 116 is fixed to a doubleacting piston 121(Fig. 4) having a rod or stem 120 and engaging a bore 1240f therespective setting member 115 so that each member 115 and the associatedmember 116 with its piston 121 are movable relative to each other. Fluidpressure may be admitted below or above each piston 121 through passages122, 123 in stem 120 to move members 115, 116 towards or away from eachother out of, or into, aligned openings 31. For example, when the par-tsare in the position shown in Fig. 2A, the locking pins 30 may bewithdrawn from the openings 31 and fluid pressure may then be admittedbetween each piston 119 and the closed forward end of its cylinder 112to shift gripping head 20 to the left in the drawings until the rearwardend of each cylinder 112 is adjacent to or engages the respective piston119. After withdrawing the setting members 115, 116 from openings 31,fluid pressure may be admitted between each piston 119 and the rearwardend of its cylinder 112 to cause pistons 119, stems 114 and heads 118 totravel to the left in the drawing substantially the length of thecylinders 112. While the stems 114 move, the gripping head 20 willremain stationary due to its large mass. Setting members 115, 116 maythen again be engaged in a selected set of openings 31 and gripping head20 may again be shifted. Any required degree of travel inwardly by head20 may thus be obtained by successively moving the stems 1:14 to theleft substantially the length of their cylinders 112 at each adjustment.

The cross-head 90 (Figs. 2B and 3B) is constructed similarly tocross-head 90, and consists of a plurality of horizontal and verticalmembers 91', 92 welded together. The cross-head abuts against the innersurfaces of the vertical outward links and is rigidly secured to thelinks by means of bolts 87' and a plate 88 bearing against the outervertical faces of the links.

As stated hereinbefore, the cross-head is provided with lateral lugs 60,61 which connect it to and carry the movable cylinders 41 to 46 (Fig.1B). Each of the lugs comprises a lateral extension of cross-head 90 forreceiving the central cylinders 42, 45, and caps 130 for mounting theupper and lower cylinders 41, 43, 44, 46, the caps being secured to theextensions 95 by means of tie-rods 131. The gripping jaw linkage (Fig.2B) of the reciprocable or force applying head 20' is carried bycross-head 90' and serves to move the jaws 10' into initial engagementwith the sheet to be stretched. When the stretching force is applied tocylinders 4146, such force will be transmittedthrough lugs 60, 61 to ym-A" the cross-head 90. The stretching force will then be applied bycross-head 9.0 to the inner faces of outward links 85' whichtransmit itto the spaced laminations 82', 83' and thus to the jaws In acorresponding way, the gripping jaw linkage 100 of the fixed grippinghead is carried by cross-head 90 and serves to move the jaws 10 intoinitial engagement with the sheet to be stretched. The stretching forceapplied to the sheet by jaws 10 is transmitted through the sheet to thejaws 10 and causes the latter to grip the sheet more firmly. The forceis then transmitted through laminations 82, 83 to outward links '85, tocross-head 90, and to pins in the oval openings 31 of girders 34, 35.The reaction forces -at 50, 51 and atpins 30 act to place the girders34, 35 under compression so that they are stressed in the manner ofcolumns. As the jaws 10, 10 bear against inclined faces of thelaminations 32, 82, 83, 83' and tend to move such faces apart from eachother when stretching forces. are applied, the inward links 84, 84 willbe subject to pull, whereas the outward links 85, 85 will be subject tocompression apart from the forces transmitted at the cross-heads 90, 90,the tension and compression stresses in the links being relativelysmall. The stress distribution in the laminations 82, 82', 83, 83' isfavorable since a stress-sustaining support in the form of inward links84, 84 is provided at a short distance from the jaws 10, 10.

It will be understood that the girders 34, 35 form a structure whichoperatively connects the gripping heads so that the frame members 14, 15are relieved from the transmission of stretching forces as known in theart. It will further be clear that, if suitable, the frame proper may beused to connect the gripping heads operatively in conventional manner.

The invention solves the problems which presented themselves in thebuilding of high capacity stretching machines:

a. By providing separate upper and lower laminated sections for eachgripping head, larger heads can be constructed than washeretoforepossible, and the stress distribution is greatly improved by thearrangement described.

12. By providing cross-heads between the upper and lower laminatedsections, it is possible to mount the pressure cylinders alongside ofand connected to the crosshead of the pressure applying, reciprocablegripping head so as to obtain a more compact machine. This avoidsmounting the cylinders a considerable distance outwardly and connectedto the reciprocable head by long links as was heretofore the practice.Likewise, the locking means for the adjustable gripping head may beconveniently connected to the cross-head thereof.

c. By providing fluid motors and range adjusting mechanisms therefor toshift the adjustable gripping head, electric motors are eliminated forthis purpose while keeping the stroke of the fluid motors withinpractical limits. The travel mechanism described can be arranged readilyon the stretching machine and connected conveniently to the cross-headof the adjustable gripping head.

Having described my invention, what I claim and desire to secure byLetters Patent is:

1. In a horizontal stretching machine having a frame, a pair of grippingheads supported on said frame for relative movement longitudinallythereof, upper and lower jaw means movable on said heads for grippingthe material to be stretched, and means for applying pressure to movesaid gripping heads away from each other, the improvement whichcomprises each gripping head having an upper section which supports saidupper jaw means and a separate lower section spaced from the uppersection and which supports said lower jaw means, each section beingcomposed of a plurality of vertical laminations, and means forinterconnecting each upper section and the respective lower sectionadjacent the inward ends of the '6 gripping heads facing each other andadjacent the other ends of the gripping heads, said interconnectingmeans including links pivotally connected at their ends to therespective upper and lower sections 2. In a horizontal stretchingmachine having a frame, a pair of gripping heads supported on said framefor movement longitudinally thereof, upper and lower jaw means movableon said heads for gripping the material to be stretched, locking meansfor securing one of said gripping heads relative to the frame inadjusted position, and means for applying pressure to the other grippinghead to move it away from the adjustable gripping head, the improvementwhich comprises each gripping head having an upper section whichsupports said upper jaw means and a separate lower section spaced fromthe upper section and which support said lower jaw means, each sectionbeing composed of a plurality of vertical laminations, means forinterconnecting each upper section and the respective lower sectionadjacent the inward ends of the gripping heads facing each other andadjacent the other ends of the gripping heads, said interconnectingmeans including links pivotally connected at their ends to therespective upper and lower sections, and a crosshead in each of saidgripping heads and secured thereto between the sections of each. head,said locking means of the adjustable gripping head and said pressureapplying means of the other gripping head being connected to therespective cross-heads.

3. A stretching machine as specified in claim 2, in which a fixed,channel shaped girder is provided at each side of said machine, the sidewalls of the channels being formed by arms of the girders, and lateralextensions are provided on said .crosshead of the adjustable grippinghead, said extensions having upper and lower portions embracing thegirders and intermediate portions protruding into the channels betweenthe arms .of the girders, and in which said arms have aligned sets ofopenings therethrough along their length, and said upper, lower andintermediate portions have one set of aligned openings therethrough ateach side of the adjustable gripping head, said locking means comprisingpins guided in the openings of said upper and lower portions and when inlocking position engaging selected openings in the arms of the girdersas well as the openings in said intermediate portions to secure saidadjustable gripping head to the girders.

4. A stretching machine as specified in claim 2, in which a fixed girderis provided at each side of said machine and has openings therethroughalong the length thereof, and in which actuating means are provided forshifting the adjustable gripping head along said frame, said actuatingmeans comprising at each side of the machine a cylinder element and apiston element cooperating therewith, fastening means for securing oneof said elements at each side to the cross-head of said adjustablegripping head, and means for releasably securing the other of saidelements at each side in selected openings in therespective girders.

5. A stretching machine as specified in claim 4, in which the means forreleasably securing one of said elements at each side to the respectivegirders includes a pair of range setting members adapted to be movedinto and out of the selected openings, guides for the members, and meansfor moving said members into said openings so as to fix said elements inadjusted position and for moving said members out of said openings so asto permit movement of said elements relative to said girders to otheropenings.

6. In a stretching machine, a frame, a pair of gripping heads supportedon said frame for movement longitudinally thereof, one of said grippingheads being adjustably locked in position relative to theframe, theother of said gripping heads being reciprocable and adapted to havepressure applied thereto to move the gripping heads relatively to eachother; each of said gripping heads having upper and lower jaw meansmovable thereon for gripping the material to be stretched, each grippinghead comprising an upper section in which the upper jaw means issupported and a separate lower section spaced from the upper section andin which the lower jaw means is supported, each section being composedof a plurality of vertical laminations, means connecting each uppersection to the respective lower section adjacent the inward ends of thegripping heads facing each other and adjacent the other ends of thegripping heads, said connecting means including links pivotallyconnected at their ends to the respective upper and lower sections, anda cross-head secured to each gripping head and positioned between thesections thereof, the cross-head of the reciprocable gripping headhaving a lateral lug at each side; a fixed cross-head mounted at eachside of the machine, and a cylinder system and a cooperating pistonsystern at each side, one of said systems at each side being secured tothe respective fixed cross-head, the other of said systems at each sidebeing secured to the respective lateral lug' of the cross-head of thereciprocable gripping head. e

7. In a horizontal stretching machine, frame means, a pair of grippingheads supported on said frame means for movement longitudinally thereof,one of said gripping heads being reciprocable towards and away from theother head, the position of said other head being adjustable relative tothe frame means, said frame means comprising a structure operativelyconnecting said gripping heads, a cylinder element and a cooperatingpiston element for shifting said adjustable gripping head relative tosaid frame means to change its position, one of said elements beingsecured to the adjustable gripping head, and means for securing theother element to said structure selectively in one of a plurality ofpositions along the length of said structure, whereby the range ofshifting movement of the adjustable gripping head may be varied.

8. A stretching machine as specified in claim 7, in which said structurehas openings along the length thereof, and said last-named meansincludes a range setting member for engaging a selected opening in saidstructure. I

9. A stretching machine as specified in claim 8, comprising lockingmeans for securing the adjustable gripping head to said structure inadjusted position, said locking means including a locking pin movableinto and out of one of said openings when not engaged by said rangesetting member.

10. A stretching machine as specified in claim 7, in which saidstructure comprises a channel shaped girder having lateral arms andaligned pairs of openings through said arms along the length thereof,and in which said last-named means includes a pair of range settingmembers adapted to engage a selected pair of openings in said girder,mechanism being provided for moving the setting members into said pairof openings to fix said other element in selected position and forwithdrawing the setting members to permit movement of said other elementrelative to the girder to another pair of openings therein.

11. A stretching machine as specified in claim 10, in which saidmechanism includes a double-acting piston attached to one of said rangesetting members, the other member having a bore in which said pistonoperates.

12. In a horizontal stretching machine having a frame, a pair ofgripping heads supported on said frame for relative movementlongitudinally thereof, upper and lower jaw means movable on said headsfor gripping the material to be stretched, and means for applyingpressure to move said gripping heads away from each other, theimprovement which comprises each gripping head having an upper sectionwhich supports said upper jaw means and a separate lower section spacedfrom the upper section and which supports said lower jaw means, eachsection being composed of a plurality of vertical laminations, and meansfor interconnecting each upper section and the respective lower section,said interconnecting means including vertical inward links disposedadjacent those ends of the gripping heads which face each other andspaced from said movable jaw means, vertical outward links adjacent theother ends of said gripping heads, and pivots connecting the ends ofsaid inward and outward links to the respective upper and lowersections, a crosshead being provided in the space between the sectionsof each gripping head in abutting relation to the respective outwardlinks.

References Cited in the file of this patent UNITED STATES PATENTS998,455 Benton July 18, 1911 1,903,638 Sykes Apr. 11, 1933 2,009,829Williams July 30, 1935 2,164,343 Nighthart July 4, 1939 2,315,971 LakeApr. 6, 1943 2,391,657 Tavelin Dec. 25, 1945 2,473,109 Schneider June14, 1949 2,523,871 Mavor Sept. 26, 1950 2,685,260 Auger Aug. 3, 19542,727,556 Albers Dec. 20, 1955 FOREIGN PATENTS 584,682 France Nov. 24,1924

